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<HTML><HEAD><TITLE>Chapter 1 -- A Global</TITLE><META></HEAD><BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#0000EE" VLINK="#551A8B" ALINK="#CE2910"><H1><FONT SIZE=6 COLOR=#FF0000>Chapter 1</FONT></H1><H1><FONT SIZE=6 COLOR=#FF0000>A Global View of Intranets</FONT></H1><HR><P><CENTER><B><FONT SIZE=5><A NAME="CONTENTS">CONTENTS</A></FONT></B></CENTER><UL><LI><A HREF="#AGlobalViewofanIntranet">A Global View of an Intranet </A></UL><HR><P>What exactly is an intranet? It's one of those terms that's morethrown around than understood, and has become more of a buzzwordthan a commonly understood idea. Simply put, an intranet is aprivate network with Internet technology used as the underlyingarchitecture. An intranet is built using the Internet's TCP/IPprotocols for communications. TCP/IP protocols can be run on manyhardware platforms and cabling schemes. The underlying hardwareis not what makes an intranet-it's the software protocols thatmatter. <P>Intranets can co-exist with other local area networking technology.In many companies, existing "legacy systems" includingmainframes, Novell networks, minicomputers, and various databases,are being integrated into an intranet. A wide variety of toolsallow this to happen. Common Gateway Interface (CGI) scriptingis often used to access legacy databases from an intranet. TheJava programming language can be used to access legacy databasesas well.<P>With the enormous growth of the Internet, an increasing numberof people in corporations use the Internet for communicating withthe outside world, for gathering information, and for doing business.It didn't take long for people to recognize that the componentsthat worked so well on the Internet could be equally valuableinternally and that is why intranets are becoming so popular.Some corporations do not have TCP/IP networks, the protocol requiredto access the resources of the Internet. Creating an intranetin which all the information and resources can be used seamlesslyhas many benefits. TCP/IP-based networks make it easy for peopleto access the network remotely, such as from home or while traveling.Dialing into an intranet in this way is much like connecting tothe Internet, except that you're connecting to a private networkinstead of to a public Internet provider. Interoperability betweennetworks is another substantial bonus.<P>Security systems separate an intranet from the Internet. A company'sintranet is protected by firewalls-hardware and software combinationsthat allow only certain people to access the intranet for specificpurposes. <P>Intranets can be used for anything that existing networks areused for-and more. The ease of publishing information on the WorldWide Web has made them popular places for posting corporate informationsuch as company news or company procedures. Corporate databaseswith easy-to-build front-ends use the Web and programming languagessuch as Java. <P>Intranets allow people to work together more easily and more effectively.Software known as groupware is another important part of intranets.It allows people to collaborate on projects; to share information;to do videoconferencing; and to establish secure procedures forproduction work. Free server and client software and the multitudeof services, like newsgroups, stimulated the Internet's growth.The consequence of that growth stimulated and fueled the growthof intranets. The ease with which information can be shared, andwith which people can communicate with one another will continueto drive the building of intranets. <H2><A NAME="AGlobalViewofanIntranet"><FONT SIZE=5 COLOR=#FF0000>A Global View of an Intranet </FONT></A></H2><P>An intranet is a private corporate or educational network thatuses the Internet's TCP/IP protocols for its underlying transport.The protocols can run on a variety of network hardware, and canalso co-exist with other network protocols, such as IPX. Peoplefrom inside an intranet can get at the larger Internet resources,but those on the Internet cannot get into the intranet, whichallows only restricted access from the Internet. <UL><LI>Videoconferencing is an important application that requiressending massive quantities of data. Intranets can be built usingcomponents that allow the extremely high bandwidths required fortransferring such information.<LI>Often an intranet is composed of a number of different networksinside a corporation that all communicate with one another viaTCP/IP. These separate networks are often referred to as <I>subnets</I>.<LI>Software that allows people to communicate with each othervia e-mail and public message boards and to collaborate on workusing workgroup software is among the most powerful intranet programs.Applications that allow different corporate departments to postinformation, and for people to fill out corporate forms, suchas time sheets, and for tapping into corporate financial informationare very popular.<LI>Much of the software used on intranets is standard, off-the-shelfInternet software such as the Netscape Navigator and the MicrosoftExplorer Web browsers. And customized programs are often built,using the Java programming language and CGI scripting.<LI>Intranets can also be used to allow companies to do business-to-businesstransactions, such as ordering parts, sending invoices, and makingpayments. For extra security, these intranet-to-intranet transactionsneed never go out over the public Internet, but can travel overprivate leased lines instead.<LI>Intranets are a powerful system for allowing a company todo business online, for example, to allow anyone on the Internetto order products. When someone orders a product on the Internet,information is sent in a secure manner from the public Internetto the company's intranet, where the order is processed and completed.<LI>In order to protect sensitive corporate information, and toensure that hackers don't damage computer systems and data, securitybarriers called firewalls protect an intranet from the Internet.Firewall technology uses a combination of routers, servers andother hardware and software to allow people on an intranet touse Internet resources, but blocks outsiders from getting intothe intranet.<LI>Many intranets have to connect to "legacy systems"-hardwareand databases that were built before an intranet was constructed.Legacy systems often use older technology not based on the intranet'sTPC/IP protocols. There are a variety of ways in which intranetscan tie to legacy systems. A common way is to use CGI scriptsto access the database information and pour that data into HTMLformatted text, making it available to a Web browser.<LI>Information sent across an intranet is sent to the properdestination by routers, which examine each TCP/IP packet for theIP address and determine the packet's destination. It then sendsthe packet to the next router closest to the destination. If thepacket is to be delivered to an address on the same subnetworkof the intranet it was sent from, the packet may be able to bedelivered directly without having to go through any other routers.If it is to be sent to another subnetwork on the intranet, itwill be sent to another internal router address. If the packetis to be sent to a destination outside the intranet-in other words,to an Internet destination-the packet is sent to a router thatconnects to the Internet.</UL><HR><CENTER><P><A HREF="contents.htm"><IMG SRC="HB.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><A HREF="#CONTENTS"><IMG SRC="CC.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><A HREF="ch2.htm"><IMG SRC="NC.GIF" BORDER=0 HEIGHT=88 WIDTH=140></A><HR WIDTH="100%"></P></CENTER></BODY></HTML>?? 快捷鍵說明
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